Yes, policy is often self-defeating. However it's not exactly cancelling out: tariffs + subsidies transfer consumption of specific products to domestic producers, tariffs alone just reduce it. Subsidies alone would raise consumption and direct it domestically.

It goes without saying this all comes at the cost of everyone who's not receiving the subsidies.

Eh it kinda makes sense.

You want to boost domestic production but you also don't want to stifle domestic adoption.

So if you implement both tariffs and subsidies, consumers can still pay the market price but will buy up all domestic production first.

This sounds correct to me? But I haven't given really thought about it deeply yet.

Those types of tariffs typically just bring foreign imports up to the domestic range, so it doesn't really mean that domestic will be adopted first. If you wanted a targeted affect, you could put tariffs on the imports and subsidize the domestic manufacturers.

Don’t the subsidies apply to all panels regardless of their origin?